There is a preliminary plan to close the entire National Mall to the public for Inauguration Day amid security concerns, ABC News has confirmed.

The Washington Post was the first to report on the development, but The National Park Service has said it will make an announcement on the Mall following ongoing discussions with the Secret Service, the Biden Inaugural team and D.C. Mayor Muriel Bowser.

Traditionally, members of the public gather on the National Mall -- bookended by the Capitol building and Lincoln Memorial -- for viewing of the inauguration on large jumbotrons.

But the Mall's potential closure comes in the wake of a violent seige on the U.S. Capitol building last week, which left at least five people dead, and amid heightened security concerns regarding armed protests being planned ahead of Biden's inauguration on Jan. 20.

Security preparations for next week have already increased with up to 20,000 National Guard troops authorized to provide security at the Capitol and around Washington, D.C., for next week's ceremony, according to a Defense Department official.

Bowser has already warned visitors to stay away from the District for the inauguration due to threats of both the coronavirus pandemic and of violence.

Editor’s Note: A previous version of this post reported that the entire National Mall would be closed to the public for Inauguration Day amid security concerns. The text has been updated to reflect the fact that the closure is only a preliminary plan.

-ABC News' Dee Carden and Josh Margolin

Arizona Gov. Doug Ducey, a Republican, has announced he will attend Biden’s inauguration after weeks of attacks from Trump for signing the certification of Arizona's election results affirming Biden's narrow win in the state.

“It doesn't matter who you supported in the election — once the election is over, we put country before party. Never has it been more important than right now to observe these traditions for the whole world to see," Ducey said in a statement Thursday.

"I was honored to represent Arizona at the inauguration of President Trump in 2017, and I am honored to represent our state at the 59th Inaugural Ceremonies next week. President-elect Biden is assuming office at a critical time in our nation’s history, and I wish him well," he added.

The Arizona Republican Party is scheduled to meet a few days later on Jan. 23, when members will vote on censuring some apparent party foes including Ducey, Cindy McCain and former Sen. Jeff Flake, R-Ariz.

-ABC News' Meg Cunningham

On one side of Pennsylvania Avenue in Washington, D.C., President Trump -- now the only president in history to be impeached twice -- faces another Senate trial following the House charging him Wednesday with one article of impeachment for "incitement of insurrection." Shortly after 10 Republicans sided with Democrats for the vote, Trump released a video from the Oval Office condemning the violence at last week's Capitol riot, which he called a "calamity," but he did not address impeachment.

On the other side of Pennsylvania Avenue stands what's now become a crime scene -- the U.S. Capitol complex. By this weekend, up to 20,000 National Guard troops, many armed, will be deployed to the area amid heightened security concerns and ahead of Biden’s inauguration. Inside the Capitol, metal detectors were installed to enter House chamber earlier this week, and House Speaker Nancy Pelosi announced plans to fine members who don't comply with the new protocol up to $5,000.

Senate Majority Leader Mitch McConnell signaled Wednesday that Trump's Senate trial should take place after Trump leaves office, saying he wouldn't call back the Senate ahead of its Jan. 19 return. McConnell also indicated Wednesday he's considering voting to convict the president, issuing a statement that says he has "not made a final decision." Pelosi has not publicly announced her timeline, but a source involved with deliberations told ABC News Wednesday she plans to send the article to the Senate next week.

Biden, reacting to Trump’s second impeachment late Wednesday, expressed his hope that the Senate will be able to maintain a bifurcated schedule, allowing the trial to move forward along with his agenda -- a message his transition has been consistent on this week. But Democrats are facing the reality that Trump is still likely to loom large over Biden's first days in office.

On Thursday evening, Biden is slated to deliver remarks on the public health and economic crises from Wilmington, Delaware, and introduce his COVID-19 vaccine and economic relief proposal. Vice President-elect Kamala Harris is expected to join.

There are no public events on Trump’s schedule.

With Trump facing a Senate trial as soon as next week, he has no organized defense team as his top lawyers have refused to represent him.

White House counsel Pat Cipollone, his deputies, and outside lawyers Jay Sekulow, and Jane and Marty Raskin are not expected to be involved.

Trump has been increasingly irritated with his personal attorney Rudy Giuliani and hasn’t been taking his calls, according to sources familiar with the matter, though Giuliani has been spotted in the West Wing recently.

And former Harvard professor Alan Dershowitz is not on board yet, though aides to the president have had discussion with him about joining the team.

Another attorney, John Eastman, whose extremist positions have troubled some members of the president’s legal team recently, is expected to take some sort of role in Trump’s impeachment defense.

Eastman represented the president in the Texas dispute and has previously pushed a racist conspiracy theory about Vice President-elect Kamala Harris.

Trump has asked top aides about how a Senate trial would look this time around. As he did during his first impeachment, Trump raised the idea of testifying himself, which aides dissuaded him from pursuing.

-ABC News' Katherine Faulders and John Santucci

Biden outlined the major points of his rescue plan: a $1.9 trillion proposal that includes a nationwide vaccination program, $1,400 checks for individuals, an extension and expansion of unemployment benefits and help for struggling communities and businesses.

Biden placed particular emphasis on housing and food insecurity and spoke about expanding SNAP benefits. He said his policy plan would extend the eviction and foreclosure moratorium, potentially previewing an executive action we could see next week. He also asked Congress to appropriate funds for rental assistance.

Biden, who preached bipartisanship while on the trail, said both he and Vice President-elect Harris had spoken with officials, mayors, and governors of both parties on a regular basis to address the problems across the country.

The president-elect also emphasized his plan's focus on helping small businesses and minority-owned businesses in particular, criticizing the Trump administration's initial approach which he said favored the wealthy and well-connected.

"Last week, I laid out how we'll make sure that our emergency small business relief is distributed swiftly and equitably, unlike the first time around. We're going to focus on small businesses, on Main Street. We'll focus on minority-owned small businesses, women-owned small businesses, and finally having equal access to the resources they need to reopen and to rebuild," Biden said.

He also pushed his plan for a mandatory federal minimum wage of $15 an hour.

"People tell me that's going to be hard to pass. Florida just passed it, as divided as that state is, they just passed it. The rest of the country is ready to move as well," he said. "No one working 40 hours a week should live below the poverty line. And that's what it means. If you work for less than $15 an hour and work 40 hours a week, you're living in poverty."

He frankly noted the "bold, practical" policy he was putting forward did not come cheap but argued there was no option to act.

"I know what I just described does not come cheaply. But failure to do so will cost us dearly," he said. "The consensus among leading economists is we simply cannot afford not to do what I'm proposing."

Biden ended his remarks with a call for unity and optimism, referencing his inauguration on Wednesday as a "new chapter for the country."

-ABC News' John Verhovek, Molly Nagle, Averi Harper and Beatrice Peterson